[en] A key to the successful design of a fusion blanket is the distribution of the amount of structural material in the first wall and the blanket enclosing structure. The first wall must support dynamic and static mechanical loads and at the same time sustain the thermal gradients and erosion resulting from the plasma heat and particle fluxes. Dynamic and static loads require high flexural rigidity, which is influenced by flow channels designed to cool the high heat flux incident on the first wall. Since the first wall temperature is roughly proportional to its thickness, thermal stresses require a thin first wall. On the other hand, a thick wall is necessary to withstand surface erosion due to particle fluxes. A fesible design must therefore represent an optimal solution satisfying such conflicting requirements